The long-term goal of the present project is to understand factors that influence throughput from single neurons in the primary motor cortex to the motoneurons that drive muscles. The primary motor cortex, through its corticospinal projection, plays a major role in controlling movements of the body. Much of this control is achieved via direct connections from single motor cortex neurons to pools of spinal motoneurons. The throughput of these connections can be assessed in spike-triggered averages of rectified electromyographic activity recorded from muscles. By recording the activity of multiple motor cortex neurons and multiple muscles simultaneously during both natural and novel voluntary motor behaviors, and analyzing their spike-triggered average effects, the present application proposes to determine whether changes in neuron firing rate and ongoing electromyographic activity during voluntary behaviors produce systematic variation in the amplitude of throughput from the neuron to the muscle. Because the firing rate of motor cortex neurons and the electromyographic activity of their target muscles often are correlated, the extent to which M1 neurons can be dissociated from that of their target muscles also will be investigated. Improved understanding of how the motor cortex controls muscles to move the body will lead to improved diagnosis, treatment and rehabilitation to functional recovery for patients affected by numerous neurological diseases including stroke, amyotrophic lateral sclerosis, multiple sclerosis, traumatic brain or spinal cord injury and cerebral palsy. PUBLIC HEALTH RELEVANCE: The long-term goal of the present project is to understand factors that influence the throughput from single neurons in the brain's primary motor cortex to the groups of motor neurons in the spinal cord that drive muscles. The connections from single motor cortex neurons to groups of spinal motor neurons play a major role in allowing the brain to control movement of the body. Improved understanding of how motor cortex neurons control muscles to move the body will lead to improved diagnosis, treatment and rehabilitation toward functional recovery for patients affected by numerous neurological diseases including stroke, amyotrophic lateral sclerosis, multiple sclerosis, traumatic brain or spinal cord injury, and cerebral palsy.